The present invention relates to a semiconductor relay, more specifically, a semiconductor relay which turn on and off high voltage at high speed.
A semiconductor relay which insulates the input and the output from each other by the optical coupling mode is known as a semiconductor relay which turns on and off high voltages by small input signals.
FIG. 5 illustrates a proposed semiconductor relay. This semiconductor relay includes a optical pulse generating circuit 100 which generates an optical pulse signal as a input signal, a light receiving circuit 110 which receives the optical pulse signal from the optical pulse generating circuit 100, a controller 120 which drives a MOSFET circuit 130 which will be described later in accordance with the received light signal of the light receiving circuit 110, and the MOSFET circuit 130 which is driven by the controller 120.
In the optical pulse generating circuit 100, one end of a resistor 102 is connected to the anode of a light emitting diode 101 and the collector of a transistor 103 is connected to the cathode of the light emitting diode 101. A DC power supply 104 is disposed between the other end of the resistor 102 and the emitter of the transistor 103. A pulse signal source 106 is connected to the base of the transistor 103 via a resistor 105.
The light receiving circuit 110 includes a plurality of photodiodes or solar cells serially connected. The light receiving circuit 110 receives and amplifies the optical pulse signal from the optical pulse generating circuit 100.
The controller 120 outputs a driving signal which drives the MOSFET circuit 130 in accordance with the optical pulse signal received and amplified by the light receiving circuit 110.
In the MOSFET circuit 130, two MOSFETs 131, 132 are inversely serially connected, and diodes 133, 134 are parallelly connected respectively to the MOSFETs 131, 132.
To the MOSFET circuit 130, a load 140 of this semiconductor relay and an AC power supply 141 to be applied to the load 140 are connected.
A driving signal is outputted from the controller 120 in accordance with a optical pulse signal generated from the optical pulse generating circuit 100, the MOSFET circuit 130 is driven by this driving signal, and a high voltage from the AC power supply 141 to the load 140 is turned on and off.
Similar circuit constitutions are disclosed in Japanese published unexamined patent application No. Hei 9-213926 and Japanese published unexamined patent application No. Hei 5-119110.
In the proposed semiconductor relay, the optical pulse signal from the optical pulse generating circuit 100 is received and amplified by the light receiving circuit 110, and the MOSFETs 131, 132 of the MOSFET circuit 130 are driven by the driving signal from the controller 120.
Consequently, the proposed semiconductor relay has a problem that large current cannot be supplied from the controller 120, and the MOSFETs 131, 132 cannot be switched at high speed.